The purpose of neutral density filters is to decrease the amount of light that enters the camera. These filters have different density of filtration (1, 2, 3 stops). When you are looking to buy one, you will ask for either 0.3, 0.6, 0.9 or 2x, 4x, 8x. The technical process that happens when a neural filter is attached, is a slower shutter speed for a given aperture or, the other way around, a larger aperture on a given shutter speed. A good tip is combining this filter with a polarizer when shooting waterfalls.

The split neutral density filter (or gradual neutral density filter) is not coated in a uniform manner (gradually change from transparent to translucent gray); otherwise, it does the same this as above explained. These types of filters have a hard edge differing from a manufacture from another. The hard edge split neutral density filters can be used in difficult exposure situations when darkness and bright light are too close and the sensor cannot capture the entire range of values (a classic example is the time of sunrise). The use of this filter will make the light areas darker, reducing the exposure difference.

Tags: neutral density filter, split neutral density filter, photo filters, photography filters, camera filters

Center-Spot filters are a type of special effects filters; they are variations of Diffusion Filters. The center of a center spot filter is usually a hole (It can also be a flat and clear glass). The hole can be round or oval. The surrounding of the hole is a diffuse glass, sometimes colored. As a result, the image taken with this filter will be sharp and clear in the middle (where the hole is), and blured around the center. It’s easy to figure out that a larger center spot filter has a larger central clear area.
Center Spot Filters can be found in 4 different types as well:
• diopters with a hole at the center
• soft spot filters with a clear center and soft-focus ring
• diffusion filters with a clear center
• densely arranged concentric circles and a clear center (ex: Cokin’s Radial Zoom)
As for the dimensions of these filters with holes, an opinion can be made from this information: Hoya’s and Tiffen’s 49mm center spot filters have a center spot of diameter about 15mm and Cokin’s Radial Zoom has a clear center of diameter 9mm.

It’s good to know that larger aperture and longer focal length will result in a more discreet and delicate result of the use of center-spot filter, and that the best results can be obtained with the Cokin Radial Zoom. Second thing to note is the fact that Hoya’s hole edge is very visible in the resulting image, which is very distracting and anaesthetic. Third thing: Tiffen’s effect is not very clear in a small image.
A similar result as the use of these filters can be obtained with a software effect called vignetting.

The following images are Hoya examples.

Center Spot

Misty Spot

Soft Spot

For Cokin examples, I recommend this site. It has a large variation of filters, each with picture example.

Tags: center spot filter, hoya, cokin, photography filter, filter, soft spot filter, center spot, soft spot, diffusion filter

Yes, I’m serious, this it’s not a joke. You can build filters for your camera (either digital or film).
And yes, it’s incredible easy.
• homemade infrared filter: a piece of developed unexposed slide film OR a floppy disk !
• homemade blue filter: a piece of exposed developed slide film with methyl blue
• homemade yellow filter: a piece of exposed developed slide film with methyl yellow

IR Filter

For obtaining the home made IR filter you need: piece of developed unexposed slide film or a floppy disk. You must go at the photo store and ask for developing the unexposed film.

The home-made filter typically begins transmission at around 710-730nm. “Congo Blue” theater gels are designed to pass IR light in order to avoid damage from heating.
When combined with red filters which block their visible blue, the combination is reported to pass the shorter wavelengths of infrared up to around 720nm.
A piece of double-side polished silicon works as an infrared filter with a relatively sharp cutoff of about 1050nm.
However, there is something else that works too: making a IR filter out of a floppy disk!
Here are some quick example photos made by a friend of mine. The interesting thing is that he had to use 13 seconds exposure and ISO 100 to get something from the candles. It’s clear that the filter is not a professional one or a useful one but it’s fun to play with it.

For this IR Filter to make “wonders” you need patience, a steady hand or a tripod and a lot of light and eventually not moving objects.
It’s very important to place the filter correct on the camera.

Andrew Davidhazy determined how and why is this infrared method really possible, and you can read his article here. Prof. Davidhazy is a Professor of Imaging and Photographic Technology at RIT, the Rochester Institute of Technology.

Colored Filter

I’m going to explain something I made about 2 years ago. I read about it in an old book my parents had about film photography and start wondering in the town asking anyone for help but they all looked at me like I was crazy.
I had a roll of 120 slide film (it’s bigger than 35mm film, but hard to find today in stores) from my parents who used to photograph with old Russian film cameras. Some frames of it were empty so I cropped them as in the images. So this part was easy.
The next thing, however, not easy anymore: I had to find “methyl blue”, “methyl green” and/or “methyl yellow”. These are chemical substance that I had no idea where should I get them from. In the end, I found out that methyl blue is used for aquariums so I provided myself (very cheap) a little bottle from a pet shop.
Then I mixed it with some water, otherwise the filter would have been very very dark, almost black.
The more water you add, the lighter the color of the filter will be. I placed the film in the prepared substance for about 5 minutes or less (depending on the concentration of the mixture). Then I turned the film on the other side to get a uniform color on both sides.

In conclusion, you can make as many filters as you want, in different tones. The only problem that remains is placing the filter on the camera. All you need to know is that you must put it very close to the lens so that the camera won’t focus on it. The rest it’s all about your imagination.

Tags: infrared filter, IR filter, home made filter, colored filter, blue filter, green filter, yellow filter, cheap fillter, free filter, selfmade filter, self made filter, inprovised filter, camera filter, photo filter, photographic filter, impovised photo filter, improvised infrared filter, improvised IR filter

An infrared filter is a filter to remove visible light and only pass infrared light in different wavelengths.
Here are some types of IR filter to choose from:
• The Kodak Wratten 87, 87A, 87B, 87C (87 starting at 750nm, 87C at 800nm, 87B at 850nm, 87A at 950nm)
• The Hoya R72 (High quality filter starting at 720nm, which includes some visible light)
• The Hoya RM90 (High quality filter starting at 900nm)
• The Hoya RM100 (High quality filter starting at 1000nm)
• The M&K 1000 (High quality filter starting at 1000nm)
• The M&K 093 and 095 (starting at 830nm)

When these filters are used together with infrared-sensitive film or sensors, very interesting “in-camera effects” can be obtained; false-color or black-and-white images with a sometimes lurid appearance known as the “Wood Effect“. There is no doubt that infrared B&W photos have some dreamlike magic as these photos tend to be even more abstract than usual B&W photos. An impressive amount of detail shines through the haze in the IR image on the right, despite the odd false-color scheme.
Notice that Objects at room to body temperatures don’t glow in the NIR any more than they do in the visible band. The 2 most commonly encountered NIR sources are the sun and incandescent (tungsten) lighting. The effect is mainly caused by foliage (such as tree leaves and grass) strongly reflecting in the same way visible light is reflected from snow.

The other attributes of infrared photographs include very dark skies and penetration of atmospheric haze, caused by reduced Rayleigh scattering and Mie scattering (respectively) in the atmosphere compared to visible light. The dark skies, in turn, result in less infrared light in shadows and dark reflections of those skies from water, and clouds will stand out strongly. These wavelengths also penetrate a few millimeters into skin and give a milky look to portraits, although eyes often look black.

In other words, generally, objects that appear quite dark at visible wavelengths may be very bright in the near IR.

Some cameras are designed to be more infrared sensitive: Minolta Dimage 7 (D7), Nikon CoolPix 950, Oly C-2020Z, Oly C-2000Z, Canon Pro70.
If you are interested in infrared photography on film camera, read this article and take this under consideration too.

Chromasoftware launched their interpretation of a Photoshop IR filter. The plug-in emulates the look of the infra-red film and it’s designed to be usable with the landscape photos as well as portraits. You can download a demo version from Chromasoftware here.

A book about infrared photography.

Tags: IR Filter , Infrared Photography, Chromasoftware, Hoya

UV radiation is invisible to human sight, but in photography it turns out to be disturbing for the image quality. An UV filter is transparent to visible light, and so can be left on the lens for nearly all shots. The UV filter absorbs ultraviolet rays without changing the exposure. With most images, most people will not see a difference when a UV filter is used.

UV sensitivity seems to vary from one digital camera to the next, but most digital cameras seem to be substantially less UV-sensitive than film. In fact, few digital cameras are UV-sensitive enough to reap a noticeable optical benefit from UV filtration, even in the most extreme UV conditions—at very high altitude (well over 10,000 feet) or in very long shots over water.

UV Filter reduces unwanted ultra-violet light and haze. Due to its multi-coated feature, it allows nearly full light transmitting into the lens which produces sharper contrast and well balanced color. Haze and skylight filters are UV variants that often carry a tint. Haze filters block more UV-A than regular UV filters but also take a bite out of visible blue. Skylight filters also cut some blue but are no more effective in the pesky UV-A band than regular UV filters.
UV and skylight filters generally require no exposure compensation, but haze filters may need a small correction. Since uniform coverage of the entire field of view is usually the intent, round UV filters make perfect sense.

Also, UV (Multi-Coated) filter protects your lens from dust, moisture & fingerprints. Actualy, this is the UV Filter most important real function.

Jay Scott explains:

Each CCD pixel has little color filter on it. These are dye filters, not dichroic, so with exposure to light—especially UV—they will gradually fade or discolor. A UV filter might possibly prolong the life of your CCD. I suspect that fading is not an issue until after the camera is obsolete, though, and it’s likely that other components will fail earlier.

More technical information after a test by photo.net:
# The Tiffen Haze-1 is best. It’s a neutral filter so color balance is unaffected.
# Next is the Tiffen 812. Good UV blocking if you also want a warming filter
# The Hoya 81B is very similar to the Tiffen 812.
# The Hoya UV filter comes next, neutral, but with 2 stops of UV blocking.
# The B+W KR1.5 gives about 1.5 stops of UV blocking with slight warming.
# The B+W and Hoya 1B aren’t very good UV blockers. The 1B is slightly warming
And the conclusion of the test is that not everyone wants a warming filter, so the clear winner for a neutral filter that really bocks UV is the Tiffen Haze-1, though the Hoya UV should also be pretty effective.

Tags: uv filter, uv multicoated filter, photo filter, camera protection, camera filter, digital camera filter, hoya, tiffen, tiffen haze

The use: A polarising filter is used to remove reflections from a shiny surface and make blue skies darker.
Types: Linear and circular polarizer. Circular is recommended.
Manufacturers: Hoya, B&W and Cokin, using different depths of filter mount.
Recommendations: not to use with wide-angle lenses and UV Filters.
A polarising filter only allows light to enter the lens in a specific direction whilst absorbing other light. If used for its traditional role of removing reflections, by polarising the light reflected from the surface it permits the actual subject to be viewed without reflections. When removing reflections the optimum polarisation effect will be achieved with the camera at a 30o ~40o angle to the subject. By rotating the polarising filter different parts of the subject can often be polarised changing the overall effect. The part of the world you are photographing will also make a big difference to the effect as the sun’s angle varies.

Polarization Filters Tips:
1. If shooting the sky near the horizon the polarisation effect will be less than if shooting the sky immediately above you.
2. Polarising filters can be used to increase the colour saturation of vividly coloured subjects.
3. Common situations when the use of polarizer is needed are the shoots of glass buildings and water surfaces.
4. By using a polarising filter, if the angles are right it is possible to cut though the landscapes haze.

Tags: circular polarizer, polarising filter, blue skies, shiny surface, hoya, Cokin, reflections